Combined developer and fixer



Patented Mar. 19, 1946 UNITED STATES PATENT OFFICE COMBINEDDEVELOPER ANDFIXER Robert Joshua King, New Canaan, Conn, assignor to The Photo.Technical Corporation, Norwalk, Conn., 'a corporation of Connecticut NoDrawing. Application July 25, 1944, Serial No. 546,581

4 Claims. (Cl. 95-'-88) This invention relates to a developer-fixer fordeveloping and fixing silver halide photographic emulsions. It relatesmore particularly'to composite solutions which both develop and fixsilver halide photographic emulsions, which are quite stable and retaintheir activity over relatively long periods of time, even when exposedin open tanks, and which give developed and fixed films substantiallyfree from dichroic fog and with no more, or little more, development fogthan is customarily obtained withordinary developing and fixingprocedures.

A number of attempts have been madeheretofore to providedeveloping-fixing solutions. In general, these have involvedthe'addition of sodium thiosulfate (hypo) to developing solutions,

usually in rather large amounts, for example, 100 grams to 1,000 cc. ofsolution, although the use of lesser quantities has been proposed. Toobtain reasonable densities with such solutions, it was found necessaryto make them quite alkaline. While the increase in alkalinity did enablethe ingredients, particularly the sodium thiosuliate and the iodide,being present in carefully regue lated amounts, with the result that thedevelop- I,

ing and fixing proceed with the production of developed pictures havinggood contrast and substantially free from objectionable fog. In somcases, it is desirable to include a relatively small quantity of alkalimetal, usually potassium, bromide in the solution to reduce developmentfog, although with some fi1ms, such as dental film, such a constituentis not necessary.

The relative proportions of the reagents used,- and the pH, of thecomposite solutions, must be carefully controlled, as it is through-theproper production of stronger images, it introduced other diificultiesincluding instability .of the solution, the production of developedpictures having a relatively'coarse grain, and the like. Attempts tostabilize the solution by the use of additives such as sugars or thelike, while they resulted inv increased stability, introduceddifficulties because of their tendency to produce dichroic fog, as didattempts to make operable solutions of lower alkalinity through the use01 lesser quantities of o. Particular difilculties inthe use ofdeveloperfixers have been encountered in connection with such films asare used in microfilm work, which have very thin layers of emulsion.

The present invention provides improved composite developing and fixingsolutions which are quite stable, that is, may be exposed even in opentanks for periods of weeks without substantial deterioration throughoxidation, which give developed pictures having good contrast and'desirable image density, with little if any more of the development fogthan is obtained with the usual developing and fixing procedures andwhich are substantially tree from dichroic fog.

The composite solutions of the invention contain an organic developingagent, usually a mixture of p-methylaminophenol and hydroquinone. afixing agent, sodium thiosulfate, one or more alkaline salts, usuallysodium carbonate, 9. preservative, usually sodium sulflte, and an alkalimetal iodide, usually potassium iodide, the pH of the solution beingcarefully regulated and the balance of the reagents and the control ofthe.

pH of the solutions'used that the desirable results obtained with thesolutions of the invention are possible. I

With respect to pH, it is necessary that the solutions have a pH whichdoes not exceed 9.5, and which is above about 8.0. Solutions with a pHin the range 8.3 to 9.0 give very good results. Particularlyadvantageous results are obtained with solutions having a pH of about8.5. The pH of the solutions is controlled by the amount of alkalinesalt, usually sodium carbonate, which is used. The quantity ofdeveloping agent, e. g., Metol, hydroquinone, or other developingagent,such as glycine or chlorhydroquinone, is about in accordance withcustomary practice in developing solutions. Thus, using mixtures ofMetol and -'a somewhat larger ratio of Metol to hydroquinone, such as 1to 2, can be used with advantage.

- hydroquinone, from 1 to 5 grams of Metol and 4 to 10 grams ofhydroquinone, per 1,000 cc. of'

solution, may be used. For the treatment of such films as are used inmicrofilm work, it is best to use not more than 3 grams of Metol per1,000 cc.

of solution, and for such films, to use the Metol and hydroquinone in aratio of about 1 to 4 or 1 to 5. With other films, such as X-ray films,

The quantity of alkali salt, such as sodium carbonate, can be variedover a relatively wide range,

- all that is required being that the quantity be such as to impart tothe solutions a' pH within the range specified above. Ordinarily around20 to 50 grams of sodium carbonate 1:01.000 cc. of solution may be used,about 30 parts giving good results, such solutions having a pH of about8.5.

Similarly, the amount of preservative or reducing agent, usually sodiumsulfite, 'canbe varied over a relatively wide range. It serves toprotect the developer against oxidation when the solution is standing,and has some part in the development. Thus the amount of sulfite may beas little as 20 grams per 1,000 cc. Too much sodium sulfite should notbe used, as excessive concentration of salts in the solutions appears tohave an adverse efiect upon the quality of the pictures finallyproduced, and thereiore it is not desirable to use more than about 50 to60 grams of sodium mum quantities of other constituents discussed above.The quantity of potassium iodide for developing-fixing solutions of theinvention may vary from 0.05 to 1.0 gram per 1,000 cc. (0.005 to 0.1%).Larger quantities introduce difilculties I through failure of the filmto fix properly.

Smaller quantities result in the production of films exhibiting dichroicfog. With certain special films, having thin emulsions, as the film formicrofilm work to which reference has been made, the limitation on thequantity of potassium iodide which may be used is even more severe, thatis, it is limited to from 0.2 to 0.6 gram per 1,000 cc. of solution(0.02 to 0.08%), variationirom this range either up or down introducingthe same type of difiiculties either with respect to dichroic fog orimproper fixing. Instead of potassium iodide, sodium iodide may be usedin equivalent quantities, but it is a somewhat more unpleasant materialto handle than potassium iodide. The amount of potassium iodide used isquite independent of whether potassium bromide is or is I not used inthe solutions. That is, the potassium iodide used is in no way ,asubstitute, in part or in whole, for potassium bromide, and theimportant functions which it performs in the specified 40 quantities inthese solutions cannot be performed by replacement of part or all of thepotassium iodide by bromide The proportions of sodium thiosuliate (hypo)I which may be used vary from about 12 to 30 grams (with 5 molecules ofwater or crystallization) to 1,000 cc. of solution (1.2 to 3.0%) Largerquantities introduce dimculties because pictures processed withsolutions containing great. concentrations of the hypo lack the contrastwhich is necessary. With smaller quantities, the solutions are notadequate fixing solutions, so that while development may besatisfactory, fixing is not.

. Potassium bromide may, and for some purposes advantageously-ornecessarily is, included in the new solutions. For the development ofordinary films at temperatures of about 68 F., the amount of potassiumbromide used may be 1 gram per 1,000 cc. or less, down to zero. I! thesolution is to be used at higher temperatures, for example, up to 85 F.the quantity of potassium bromide used may be increased, up to about 4grams per r 1,000 cc. With such films as are used in microfilm work,about 2 grams per 1,000 cc. of solution is sumcient even fortemperatures up to 85 F. .or even somewhat higher. The potassium bromidefunctions to cut down development fog. It is important, for this reason,in microfilm, and much other development work, but is not particularlyimportant for the development 0! such films as dental x-ray It may bereplaced by sodium bromide, but sodium bromide is not as easy to handleas is potassium bromide.

The solutions may be provided in the form of concentrates, containing agood deal less water than is used in the developing solutionsthemselves, and which may be diluted for use. Alternatively, the dryreagents may be dissolved in water to form the developing solution intheusual way. Little difiiculty is encountered'in dissolving the reagentsbecause of the relative dilutenessof the solutions.

Other conventional ingredients, such as alcohol or the like, may beincluded in the developing solutions, particularly where they areprovided in concentratediorm. V

In use, the developing-fixing solutions of the invention accomplish boththe developing and fixing in a single operation, eliminating the needfor care with respect to the time of treatment, as it is simplynecessary to immerse the film in the solution for a sumcient period oftime to permit the development and fixing to take place. It is notnecessary to remove the film promptly after developing and fixing,because over-development does not take place. For this reason, thesolutions are well adapted for use in apparatus for the mechanicalprocessing of film. such as are used with advantage in microfilm work,for the development of dental or other X-ray pictures,

example, but it is not limited solution for use with microfllmisprepared from the following:

Grams Sodium sulfite 40 Sodium carbonate (NaaCOa.1H:O) 30 Metol 1Hydroquinone 5 Potassium bromide 2 Potassium iodide .5 Hypo(NazSzOzfiHzO) 1 13 The solution is made up to 1,000 cc. It iselfectiv'e for the developing and flxin'g of microfilm even attemperatures as high as F. or somewhat higher.

- I claim:

l. A combined developing and fixing solution for silver halidephotographic emulsions including a developing agent, an alkaline salt. apreservative, and from 0.005 to 0.1% of alkali metal iodide and 1.2 to3.0% of sodium thiosulfate (calculated as NaaSzOz.5Hz0), said solutionhaving a pH between about8.0 and about 9.5.

2. A solution as in claim 1 which in addition contains a small quantityof alkali metal bromide.

- 3. A developing and fixing solution for silver halide photographicemulsions including a developing agent, an alkaline salt, apreservative.

from 0.02 to 0;06% of potassium iodide and from 1.2 to 1.8% of sodiumthiosulfate (calculated as NazSzOaSHzOl. said solution having apHbetween about 8.3 and about 9.0.

' 4. A solution as in claim 3 which in addition contains a smallquantity, not in excess of about 0.2% of alkali metal bromide. 7

ROBERT JOSHUA ENG.

The invention will be-further illustrated by the

